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Two commonly used terms are MPLS LDP and RSVP-TE. While the former relates to easy provisioning in MPLS setup, the latter i.e. RSVP-TE is related to guarantee bandwidth for traffic communication. LDP setups LSPs based on routing data, whereas RSVP setups additional traffic engineered LSPs.
What is LDP?
LDP is an abbreviation for Label Distribution Protocol that defines a set of process and messages by which one LSR (Label Switched Router) informs another of the label bindings. LSR further establishes label switched paths through a network by mapping network-layer routing information to data-link layer path.
In the case of MPLS LDP, Label bindings are established automatically for specific FECs (behaviour is different by different vendors).
Pros
- Easy to implement
- Scales well with large networks
- Minimal manual configuration
Cons
- No control over traffic paths
- Cannot reserve resources or guarantee QoS
What is RSVP-TE?
RSVP-TE is used to establish MPLS transport LSPs for meeting traffic engineering requirements. It is mainly used to provide QoS and load balancing across the network including optical Core network.
The RSVP-TE (traffic extension) protocol is an addition to the RSVP protocol with extensions to allow it to set up optical paths in an agile optical network.
RSVP is the primary choice if we need to perform Traffic Engineering i.e. FRR, DiffServ-TE, Explicit Routing etc.
Pros
- Full path control
- Supports bandwidth reservation and QoS
- Enables fast reroute (FRR) for high availability
Cons
- More complex to deploy and maintain
- Requires more processing and signaling overhead
Comparison: LDP vs RSVP
Below table differentiates between MPLS LDP and RSVP(-TE):
| PARAMETER | LDP | RSVP |
|---|---|---|
| Abbreviation for | Label Distribution protocol | Resource Reservation Protocol |
| Provisioning | Easy to configure. We just need to enable on interfaces. Label bindings automatically established for specific FECs | Complex configuration |
| Topology | LSPs from multiple ingresses use the same label to reach the egress (multi-point to point LSP) | RSVP sets up independent point to point LSPs. |
| QoS | Limited | Guaranteed resources |
| LSP setup initiation | Egress initiates the LSP setup | Ingress initiates the LSP setup. |
| Requirement | If primarily LSPs need to be set up, LDP should be used | If you require traffic engineering and resources reservations, use RSVP (-TE). |
| Scalability | High | Low |
| ECMP | Possible | Not Possible |
| Fast Reroute (FRR) support | No | Yes |
| IGP based decision making | LDP follows IGP for decision making | RSVP does not follow the IGP, and take independent decisions on the reserved traffic |
Download the difference table LDP vs RSVP
Which one to choose?
Choosing between LDP and RSVP-TE depends on multiple factors like: network’s complexity, performance requirements, and operational goals. LDP is perfect for straightforward, scalable MPLS deployments where simplicity and ease of use are key. On the other hand, RSVP-TE is the best choice for environments where traffic engineering, resource reservation, and path control are essential.
Related – MPLS vs IP Routing
ABOUT THE AUTHOR
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